Electrical Spin Injection and Transport in Two-Dimensional Carbon Materials

Abstract

Graphene is a promising material for spintronics. As graphene itself is usually non-magnetic, high-efficient spin-injection from a ferromagnet is necessary, which is boosted by an insulating contact barrier. However, the large contact resistance poses problems to high-frequency applications. In this context, the possibility of forming a spin efficient contact with a moderate resistance is explored by inserting a Cu layer between the ferromagnet and graphene to make use of the non-ohmic Cu/graphene contact. Clear enhancement of spin-injection efficiency was demonstrated as compared to other graphene spin valves incorporating transparent contacts in literature, and the contact resistance remains significantly lower than tunnel contacts. Besides being employed as a non-magnetic channel, graphene can be theoretically made magnetic through edge engineering. We attempted to probe this edge magnetism using a Ni-carbon nanowall nanocontact. Large magnetoresistance-like features were observed, but they are attributed to mechanical origins. These results proof that ballistic magnetoresistance reported in literature is due to artifacts.